The reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIM-l) is an important target for drug therapy in the treatment of AIDS. Despite the recent successes, several of the most important anti-RT drugs are relatively toxic and all of them select for resistant variants of the virus. We believe that a better understanding of the structure and function of HIV-1 RT would be useful in the design of more effective inhibitors. This project is part of a larger collaborative effort to understand the mechanism(s) of drug resistance of HIV-1 RT. We will use recombinant DNA techniques to express both wild-type and mutant RT. Purified RT (both mutant and wild-type) will be prepared and used for biochemical, biophysical and structural analysis (the structural analysis will be done in the laboratory of Dr. Edward Arnold). We can also supply recombinant HIV-1 RT to Dr. Parniak as needed. We have developed a system using a one-round HIV-1 vector to measure the effects of mutations in RT or in the genome on DNA synthesis in infected cells. The in vivo HIV-1 vector experiments have been designed so that we can follow specific steps in reverse transcription; this should make it possible to compare results obtained in vitro with purified mutant RT and the effects of these RT mutants on viral replication.